Femoral neck fracture, subcapital, undisplaced or impacted
In subcapital fractures with little or no displacement, the contact between the head and the neck is always maintained. One subgroup comprises fractures with the head impacted in valgus, the other consists of undisplaced fractures. These subgroups can be further divided according to the degree of posterior tilting of the femoral head.
The undisplaced fractures are unstable prior to fixation since there is no impaction.
For proper radiological evaluation x-rays in two planes at 90° to one another are necessary. In the presence of a fracture, the lateral radiograph is obtained by taking a so-called cross-table view. If this is of good quality, it will allow the surgeon to assess the degree of retroversion and the degree of fragmentation of the posterior cortex.
The Pauwels classification can best be determined intraoperatively, once traction is applied, and the fracture is reduced. After this, choice of fixation is easier. On an AP fluoroscopic view, assess the inclination of the fracture line. Pauwels type I is a fracture with <30º from the horizontal. Type II is 30º-70º from the horizontal. Type III is >70º from the horizontal.